The present invention relates to a new and improved caliper brake having a new and improved automatic adjusting mechanism wherein the brake clearance can be precisely increased or decreased manually from a point exterior of the brake while the brake is in operative position on the vehicle on which it is installed.
A number of designs of rotary cam actuators for caliper brakes have been provided by the prior art and which suffer from a number of adjustment and maintenance difficulties. In the type of actuator with which we are concerned, the brake lining is squeezed against the rotating disc by a threaded post that in turn is engaged by a threaded nut that in turn is axially driven by a rotary cam mechanism. In some of these mechanisms, the rotary drive structure for the cam is in sliding contact with portions of the nut, and when corrosion occurs or dirt enters the structure, the nut may bind to the rotary drive structure so that it may drive the nut in both directions over the threaded post thereby preventing proper clearance adjustment.
In other types of these structures, the connection between the nut and the rotary drive structure is such that the post is held stationary while the nut is adjusted both manually and automatically to control brake clearance. In some of these structures, the nut cannot be backed off manually to increase clearance in the brake without removing it from the vehicle in which it is installed.
In some other types of these brakes mechanisms, it is possible to retract the post to such an extent that the nut becomes jammed onto the threads of the post with such severity that the automatic adjusting portion of the brake slips without making an automatic adjustment of the brake. Where such structures are actuated by air pressure, or other mechanism wherein the actuating lever movement is not proportional to the brake applying movement, the lack of adjustment is not sensed by the driver, and unequal brake applications can occur.
In still other types of these structures, hard to seal passages lead through the housing to the adjustment mechanism and/or the threaded nut extends externally of the housing where corrosion can freeze the nut if rubber diaphragm type covers because damaged or do not seal for any reason.
An object of the present invention, therefore, is the provision of a new and improved automatic adjuster of the above described type which cannot be manually adjusted to a point making the automatic adjusting mechanism become inoperative.
Another object of the present invention is the provision of a new and improved automatic adjuster of the above described type wherein the threaded brake actuating post is engaged by a threaded nut that in turn is moved axially by a rotatable cam mechanism and in which the threaded nut is held against being rotated in a direction which would retract the threaded post.
A still further object of the present invention is the provision of a new and improved caliper brake in which the rotary drive mechanism for the rotary cam is out of sliding engagement with the threaded nut.
Further object and advantages will be apparent to those skilled in the art to which the invention relates.